In the manufacture of printed circuit cards and boards, a dielectric sheet material is employed as the substrate. A conductive circuit pattern is provided on one or both of the major surfaces of the substrate.
In order to provide electrical connection between layers, metal coated through-holes are provided. In providing a connection of conductive patterns through a dielectric material, to a large extent, a conductive land and line are provided on the surface of the dielectric material. However, the presence of a land is undesirable on the dielectric material since it takes up valuable area on the dielectric material which could be used for other purposes.
Accordingly, techniques have been suggested for providing landless through-hole connections. Such techniques include those suggested by Crimi, et al. in IBM Technical Disclosure Bulletin, Vol. 9, No. 10, March 1967; Mead, IBM Technical Disclosure Bulletin, Vol. 13, No. 1, June 1970; and Chumbres, et al., IBM Technical Disclosure Bulletin, Vol. 15, No. 10, March 1973.
These suggested techniques, for the most part, require some photoresist process to define the desired circuitry and/or to protect circuitry already present after the through-holes have been provided. This necessity to protect areas significantly complicates the process.